Rick Perry has tumbled by more than 20 percentage points over the past month among Republican presidential primary voters and is now second to Herman Cain, who leads the field with 28%.

Mitt Romney received little benefit from Perrys fall, garnering 17% of the vote for third place…

These results are from an IBOPE Zogby interactive pollconducted Sept. 23-26…

Note the dates of the Zogby poll. It just finished today, so while this is clearly a direct reaction to Cain’s earth-shattering Florida straw poll win, many of the voters were sampled before Cain’s incredibly powerful speech to the Presidency 5 delegates and the past 48 hours’ media circus.

UPDATE: Say what you want about Zogby’s methodology, but here’s a Fox News poll, released this evening, that uses traditional live telephone polling, and it shows Romney, Perry, and Cain neck and neck and neck with each other: